1. Field of the Invention
The invention relates generally to electrical switching apparatus and, more particularly, to electrical switching apparatus, such as circuit breakers. The invention also relates to push-to-trip assemblies for electrical switching apparatus.
2. Background Information
Electrical switching apparatus, such as circuit interrupters, generally include at least one pair of separable contacts which are operated either manually, by way of a handle and/or another suitable manually operated trip actuator accessible on the exterior of the circuit interrupter housing, or automatically by way of a trip unit in response to a trip condition (e.g., without limitation, an overcurrent condition; a relatively high level short circuit or fault condition; a ground fault or arc fault condition).
FIG. 1 shows a molded case circuit breaker 1 employing a manually operated trip actuator in the form of a push-to-trip assembly 3. The push-to-trip assembly 3 includes a push-to-trip button 5 having a first end 7, a second end 9 disposed opposite and distal from the first end 7, and a biasing element 11 (e.g., spring). The first end 7 of the push-to-trip button 5 is accessible at or about the exterior 13 of the circuit breaker housing 15 (partially shown in phantom line drawing). The spring 11 biases the second end 9 of the push-to-trip button 5 toward the exterior 13 of the circuit breaker housing 15. When the push-to-trip button 5 is pushed inward, against the bias of the spring 11, the second end 9 cooperates with the trip bar 17 of the circuit breaker 1 to cause the circuit breaker operating mechanism 19 to trip open the separable electrical contacts 21,23 (partially shown) in response to a trip condition.
Among other disadvantages, it is difficult to hold the various components (e.g., without limitation, push-to-trip button 5; spring 11; trip bar 17) of the push-to-trip assembly 3 and/or circuit breaker 1 together during assembly of the circuit breaker 1. Specifically, the push-to-trip button 5, which is spring-biased, is dependent on an external stop such as, for example, the housing 15 (e.g., cover) of the circuit breaker 1 to hold it in place. Further complicating the assembly process is the fact that the spring 11 also, directly or indirectly, biases the trip bar 17 of the circuit breaker 1. Specifically, absent a suitable stopping mechanism for resisting undesired rotation of the trip bar 17, it is difficult to achieve the desired orientation of the trip bar 17 during assembly of the circuit breaker 1. For example, assembly of the circuit breaker 1 is reliant upon the trip bar 17 abutting bimetal 25 of circuit breaker heater assembly 27. It would be preferable to avoid such abutment. Moreover, in circumstances where the push-to-trip assembly 3 and/or the trip bar 17 is/are assembled and installed in the circuit breaker 1 before the installation of the heater assembly 27, the bimetal 25 is not available for use as a stop to resist over rotation of the trip bar 17.
There is, therefore, room for improvement in electrical switching apparatus and in push-to-trip assemblies therefor.